Tesla Wall Connector gen 3 - DIY Repair

[edsonedson]

I started experiencing issues with my gen3 Tesla Wall Connector. It would start charging and then immediately stop, the Tesla logo on the charging port would flash red. I decided to take the wall connector apart to investigate further.

After doing a visual inspection on the board, I noticed the power pins on the relays that deliver the charging current to the vehicle had signs of overheating. It sort of looked like burn marks. I actually went ahead and opened the casing on one of the relays, trying to get a better look inside. I find it kind of surprising that the legs inside the relay are so thin, you would think they would design them to be thicker, preventing overheating.

Anyways, I decided to attempt a repair. What I did was, remove both power relays and replace them with new ones that I found online. I realize they are the same and I wonder if they won't inevitably fail the same way in the future. Still, I thought it was worth a shot. Alternatively, I thought about adapting a more chunky relay on the board, but the transparent cover of the wall connector leaves no room for a bigger relay.

After soldering in the new relays, it has been working well for a couple of charging sessions at full 48A. I'll continue to test it, to see how long my DIY repair will be good for. If you're interested, I captured a video of how I did the repair and posted it on my YouTube channel here:

 

[jjrandorin]

How old was your gen 3 wall connector? I know the first couple of revisions seemed to have lots of overheating issues. One of our active members did a write up on the overheating, and I believe they found similar results as you did.

Gen3 HPWC disassembly, with overheating issues explained!

Caution: Wall of text ahead! So, I got a secondhand Gen3 HPWC (TPN:1457768-01-F) that had known issues at full power and of course ran it right up to 48 amps to see what she'd do(note it had updated firmware). For a little while it did 48 amps, but after a half hour in my 20f garage, it...

teslamotorsclub.com

 

[edsonedson]

I have a TPN as follows: 1457768-00-F

 

[davewill]

With the burnt look of the PC board, I'd have probably added jumper wires to the back of the board to parallel the traces that carry the charging current. Couldn't hurt.

 

[cali8484]

What's the rating of the relays? The heat discoloration pattern suggests the overheating occurred inside the relays. For 48A charging, the relays should be rated for 60A or higher for long life. The bus bars connecting to the relays look hefty and appear to be fine.

 

[edsonedson]

What's the rating of the relays? The heat discoloration pattern suggests the overheating occurred inside the relays. For 48A charging, the relays should be rated for 60A or higher for long life. The bus bars connecting to the relays look hefty and appear to be fine.

40A rating on the relays, although there are 2 in parallel

 

[cali8484]

40A rating on the relays, although there are 2 in parallel

Those relays look like SPST relays which means 40A on each 120V phase leg so it's still only 40A at 240V. If the rating is true then the relays are not safe for sustained 48A charging at all. It would explain the overheating issues reported.

 

[Eric33432]

Those relays look like SPST relays which means 40A on each 120V phase leg so it's still only 40A at 240V. If the rating is true then the relays are not safe for sustained 48A charging at all. It would explain the overheating issues reported.

Each relay has two small pins for the coil and 4 for the contacts so they might be DPST relays.

 

[cali8484]

Each relay has two small pins for the coil and 4 for the contacts so they might be DPST relays.

I agree they could be DPST relays. Assuming they are, it's still a poor design practice as physically separate relays will never open/close at exactly the same time so current sharing will not be balanced. Over time that could degrade the contacts of one relay more than the other leading to further current sharing imbalance and overheating.

 

[davewill]

I agree they could be DPST relays. Assuming they are, it's still a poor design practice as physically separate relays will never open/close at exactly the same time so current sharing will not be balanced. Over time that could degrade the contacts of one relay more than the other leading to further current sharing imbalance and overheating.

The relays should never be carrying significant current when closing or opening. The car commands them to close, checks the voltage, then starts drawing current. Same when you press the button to remove the plug, the car stops drawing current, then commands the relays to open (or the removal of the plug causes them to open). That's part of the J1772 spec.

 

[cali8484]

The relays should never be carrying significant current when closing or opening. The car commands them to close, checks the voltage, then starts drawing current. Same when you press the button to remove the plug, the car stops drawing current, then commands the relays to open (or the removal of the plug causes them to open). That's part of the J1772 spec.

Current sharing imbalance across the relays can still be significant regardless. Also, AFAIK, the J1772 spec does not specify limit for inrush current when the relays close which can be very high even before actual charging starts.